LONDON >> For 34 matches over 41⁄2 months, on hard, clay or grass courts, Serena Williams was unbeaten — and, in the minds of many, unbeatable.

So it was apt, somehow, that the longest winning streak in women’s tennis since 2000 would end at this memorably unpredictable edition of Wimbledon, where up is down, where seedings and pedigree mean nothing whatsoever, where even five-time champion Williams looked lost at the start and, most surprisingly of all, the finish of her fourth-round match.

Stumbling on the Centre Court grass a couple of times while her game slumped in crunch time, the No. 1-ranked and No. 1-seeded Williams dropped the last four games to bow out 6-2, 1-6, 6-4 Monday against 23rd-seeded Sabine Lisicki of Germany.

“Didn’t play the big points good enough,” said Williams, who had won three of the past four Grand Slam titles, including Wimbledon a year ago and the French Open less than a month ago. “I didn’t do what I do best.”

Oddly passive down the stretch, Williams essentially let Lisicki do what she does best: dictate points quickly with a big serve, powerful returns and pinpoint groundstrokes. If that sounds familiar, could be because it’s the formula Williams uses to dominate her sport. Except on this breezy afternoon, Lisicki compiled a 10-7 edge in aces and a 35-25 lead in winners, and broke Williams five times.

“Come on, guys, let’s get with it. She’s excellent,” a composed Williams said at her news conference after blowing leads of 3-0 and 4-2 in the third set. “She’s not a pushover.”

Especially at Wimbledon. Her game is built for grass. Lisicki is a mediocre 16-15 at the other three Grand Slam tournaments and 17-4 at the All England Club. She reached the semifinals at Wimbledon in 2011, and is into her fourth quarterfinal, coincidentally beating the reigning French Open champion every time: Svetlana Kuznetsova in 2009, Li Na in 2011, Maria Sharapova in 2012, and Williams in 2013.

“Good omen,” Lisicki said.

“Obviously,” she said, “I went into the match feeling that I could win.”

Might have been the only person who felt that way. After all, Williams owns 16 major championships, and entering Monday, the 31-year-old American had won 46 of 48 matches this season, and 77 of 80 since the start of Wimbledon in 2012.

“You cannot be perfect, every match, all year,” said Patrick Mouratoglou, the French coach who began working with Williams last year. “She won 34 matches in a row. It has to stop one day. It has to happen. And it happened today.”

The inevitability of failure, even for the most successful player, has never been made clearer than during this tournament. This was only the first day of the fortnight’s second week, yet Williams joined quite a list of those already gone: Roger Federer, Rafael Nadal, Victoria Azarenka and Sharapova — all major title winners, all former No. 1s, all out by the end of Day 3.

“This,” summed up 17th-seeded Sloane Stephens, “has been a crazy Wimbledon.”Sure has. No U.S. men reached the third round, something that last happened 101 years ago, and Williams’ departure made Stephens the lone American singles player left. The 20-year-old Stephens’ first quarterfinal at the All England Club comes Tuesday against No. 15 Marion Bartoli of France, the 2007 runner-up.

The other matchup on their half of the draw is No. 8 Petra Kvitova of the Czech Republic, the 2011 Wimbledon champion, against No. 20 Kirsten Flipkens of Belgium. Tuesday’s remaining quarterfinals are No. 4 Agnieszka Radwanska of Poland, who lost to Williams in last year’s final, against No. 6 Li of China; and Lisicki against 46th-ranked Kaia Kanepi of Estonia.

Kanepi reached her fifth Grand Slam quarterfinal, and second at Wimbledon, with a 7-6 (6), 7-5 victory over 19-year-old Laura Robson, the first British woman in the fourth round at the All England Club since 1998. Robson, like others, took note of Monday’s most significant outcome.

“I thought for sure Serena was going to win the tournament,” Robson said, expressing a popular sentiment.

On Wednesday, the men’s quarterfinals on the draw’s top half are No. 1 Novak Djokovic of Serbia, a six-time Grand Slam titlist and the only remaining past Wimbledon winner, against No. 7 Tomas Berdych of the Czech Republic, the 2010 runner-up; and No. 4 David Ferrer of Spain against No. 8 Juan Martin del Potro of Argentina, the 2009 U.S. Open champion. On the bottom half, it will be No. 2 Andy Murray of Britain, the London Olympic gold medalist and 2012 U.S. Open winner, against 54th-ranked Fernando Verdasco of Spain; and No. 24 Jerzy Janowicz against his Davis Cup teammate and pal, 130th-ranked Lukasz Kubot, in a match between the first two Polish men to reach a Grand Slam quarterfinal since 1980.

One will give the country its first male semifinalist at a major tournament.

“We hugged. We are happy,” Janowicz said. “Magical.”

Janowicz’s serve reached 137 mph and his temper flared on occasion as he beat 37th-ranked Jurgen Melzer 3-6, 7-6 (1), 6-4, 4-6, 6-4, while Kubot also won a five-setter, celebrating with a can-can dance routine after hitting 26 aces to eliminate 111th-ranked Adrian Mannarino 4-6, 6-3, 3-6, 6-3, 6-4.

Both Janowicz and Kubot benefited from one of the record-equaling 13 withdrawals or mid-match retirements last week, another element fueling the tournament’s topsy-turvy feel.

“Everyone was a bit on edge, a little bit uptight, because of what was happening with the injuries, withdrawals, upsets and stuff,” said Murray, who like Djokovic hasn’t lost a set. “Obviously, Serena losing today is a major shock, as well.”

Late Monday afternoon, British bookmakers were making Lisicki the favorite to win a trophy that hours earlier seemed destined for Williams. Asked whether that affects her in any way, Lisicki shot back: “No, not at all.” Not even a little bit? Lisicki didn’t blink and answered, “No.”

It was the same steely demeanor the quick-with-a-smile Lisicki displayed at key moments on court, weathering a near-collapse in which Williams grabbed nine consecutive games to take the second set and go up 3-0 in the third.

“I just was fighting for every single point,” Lisicki said, “no matter what was happening out there.” 
Williams hadn’t lost a match anywhere since her three-set defeat against Azarenka in the final of the Qatar Open on Feb. 17. She hadn’t even lost a set since the French Open quarterfinals against Svetlana Kuznetsova on June 4. But Lisicki showed things would be different Monday with an early five-game run, including when she smacked a forehand return winner to break at love and take the opening set.

Lisicki yelled, “Come on!” The crowd, eager to see something special, roared. Williams walked to the sideline slowly, stunned.

“I just was thinking, ‘Let’s get to a third set,”’ Williams said. “That’s what I always say when I lose a first set.”

Going from considerable trouble to total control, as if simply by wishing to do so, Williams produced 43 masterful minutes in which Lisicki did not win a single game. Williams did not have an unforced error in the second set, and she even got some unneeded assistance early in the third, with two consecutive return winners that both clipped the net tape and bounced over.

“I felt,” Williams said, “that I was on the verge of winning.”

Lisicki finally ended the drought by holding to 3-1 with one of her four second-serve aces in the match, then a 115 mph service winner.

“Huge serves,” Williams said. “Constantly, constantly, back-to-back-to-back.” 

That’s how her opponents usually feel. But Lisicki managed to get better reads on returns late, and broke to get within 4-3 with a forehand passing winner as Williams lost her footing and fell to her knees. The next game was key. Lisicki fell behind love-40, meaning Williams had three break points, any of which would give her a 5-3 lead and allow her to serve for the match.

But Lisicki wouldn’t fold.

“I put more pressure on her,” she said. “I started to be more aggressive again.”

One missed backhand by Williams, then a pair of winners by Lisicki, erased the break points, and she wound up holding with a 95 mph ace and 115 mph service winner. At 4-all, deuce, Lisicki hit a forehand passing shot after Williams tripped, making it break point. Williams then awkwardly sailed an overhead long, putting Lisicki ahead 5-4.

Suddenly serving for the biggest win of her career, Lisicki double-faulted to give Williams a break point — and an opening. But it was Lisicki who closed strongly, hitting a 113 mph ace and a 99 mph service winner, and then ending a 17-stroke exchange with a forehand winner.

Lisicki dropped to her knees near the net, covering her face as tears flowed.

Williams was asked whether the pressure to win got to her.

“Not at all,” she said. “I mean, every time I step out on the court, I’m the favorite.”

That sort of thing hasn’t mattered one bit at this Wimbledon.